Painting With Light: Strobe Emulation For Underwater Imaging

The impossible Challenge

There is perhaps no field in photography that offers a greater variety of challenges than filming underwater. Imagine a place devoid of gravity, where form and motion are unbounded by the constraints of the surface world. Where the life around you is in constant motion, turbulent and ever-changing with each passing moment. In this endless whirl of currents and creatures, its sheer vastness stuns the imagination. It’s staggeringly beautiful, yet devoid of warmth or air, one of the most hostile environments to human life. Here, nothing is as it seems; while light and color on land behave as one would expect, they undergo some remarkable transformations beneath the surface. For one, the optical nature of water magnifies everything by more than a 1/3, altering your very perception of space and distance in an already alien realm.

However, even stranger is its effect on color. As you descend, color rapidly begins to fade. Reds disappear first, then orange, then yellow, until the world is left in shades of blue and green. Light flattens, contrast dulls, and what was once vivid becomes muted. Therein lies the biggest challange of all—capturing a world that actively erases itself. Traditionally, strobes have been the solution, restoring lost colors and contrast. But strobes are expensive, bulky, and not always practical. With new technologies and computational techniques, we can now push images further than ever before—beyond the limitations of the tools we may not have.

The method I’ve developed uses careful object masking and light painting in Camera RAW and Photoshop to relight images in post. By selectively sculpting highlights and shadows, natural-light shots can take on a more dramatic, dimensional quality, mimicking the depth and contrast of strobe photography. It’s not a perfect substitute, and it has its own limitations (as we’ll see later), but for those who don’t have access to expensive lighting setups, it offers a powerful alternative—one that can allow you to bring life to your images in a whole new way.

A Word Of Warning

As with any work of art, the key is having a strong base to build on – even the most technically elaborate editing will rarely save a blurry or badly composed shot-no matter how badly you want it to. And trust me, I’ve been there MANY times; it’s probably the “rookiest” of rooky mistakes. You think you’ll just “fix it in post” only to find that you’re favourite shot is just a backscattery mess. The solution? GET THE SHOT RIGHT THEN AND THERE. Nail your focus, your framing, your exposure, everything that makes the image from the moment you press the shutter. Not only will it save you hours (and yes, I mean LITERAL hours) trying to fix your mistakes, but it’ll make all the steps we’ll follow much easier.

Step 1: Cleaning The Image & Global Edits

Before relighting, we need a strong base image: well-exposed, balanced, and clean. The goal is to restore detail without flattening contrast too much.

• White Balance – Adjust to restore natural tones and counteract excess blue/green cast. Start with a neutral setting and fine-tune based on the subject’s natural coloration.
• Exposure & Contrast – Bring back overall brightness without blowing out highlights. The goal is a balanced exposure that retains shadow depth.
• Shadows & Highlights – Lift shadows slightly to recover details while keeping highlights controlled. Avoid making the image look artificially HDR.
• Texture & Clarity – Texture enhances fine details (scales, skin, eyes), while Clarity boosts midtone contrast. Use sparingly—too much can introduce unwanted artifacts.
• Dehaze (if needed) – Lightly used, this can help cut through murky water.

Once the base adjustments are made, the real work begins—relighting the subject.

Step 2: Isolating The Subject

To mimic the directional effect of strobes, we need precise control over light falloff. This starts with isolating the subject using CameraRAW’s Object and Brush Selection tools.

1. Use Object Selection – Instead of “Select Subject,” use Object Selection for more controlled, accurate masking—especially useful for marine life. Note: If parts of the subject aren’t detected or selected incorrectly, you can add or subtract from the selection accordingly by painting on the desired area (for this parrot fish shot, parts of the fins were left out so I had to add 2 more objects)

Refine with the Brush Tool (apply when nessecary– If need, you can further Fine-tune the mask using the Brush Selection Tool, painting in key details like fins, tentacles, and soft textures if object selection doesn’t detect a given area.

• 2. Invert the Mask-Duplicate and Invert the mask by right clicking on the selection or pressing Ctrl +K to create a copy of the subject selection for additional adjustments while separating the background for editing

• 3. Turn Down Exposure, Boost Blacks – The trick here is to reduce background exposure aswell as amplifying the blacks. Depending on how strong you want the effect to be, this creates a subtle or more prominent falloff from the background (which, though not yet fully realistic because of the hard edge around the subject), gives the illusion of background seperation much like you’d get from distancing your strobe from the water column.

Step 3: Creating Fall-off With Gradient Masks

Now that the subject is isolated, we need to shape the light falloff—giving the illusion that a strobe was placed at a specific angle. Note that the number of masks needed depends on the kind of subject you’re lighting as well as the aesthetic your aiming for (bright over moody, naturalisti over dramatic) so adapt accordingly.

1. Create a Radial/Linear Gradients
   • Use Gradient Masking in CameraRAW to apply a subtle radial or linear light fade by darkening the exposure
   • This mimics how strobes cast directional lighting and help the subject blend more smoothly with the background
2. Adjust Exposure and Highlights
   • Increase exposure slightly on the side where light would naturally hit.
   • Reduce shadows on the opposite side to maintain depth

3. Refine for Realism

• Use multiple gradients if needed—one for key light, another for rim light.
• Keep adjustments subtle—overdoing it can make the subject look artificial. Adjusting the strength of the mask’s effect can be done by controling the “Amount” Slider on the right, similarly to layer opacity in photoshop.

With proper gradient masking, the subject should look more three-dimensional, with lighting that feels directional, rather than flat.

Step 4: Removing Masking Artefacts (If Nessecary)

No matter how precise your masking, small fringes, artifacts, or unnatural feathering can appear along the edges. Also, underwater images often have backscatter—floating particles illuminated by ambient light.

How to Fix Masking Errors

• Use the Remove Tool – If fringing or ghosting appears around the mask, remove it directly in Photoshop using the Remove Tool for seamless blending.
• Fix Color Spillage – If the subject’s edges still have excess blue/green or show abberration, adjust the Color Mixer and Color Noise slider in CameraRAW to neutralize it.

Cleaning Backscatter in Photoshop

• Use Spot Healing Tool to remove visible floating particles.
• If needed, apply a low-opacity Clone Stamp Tool for more complex areas.

At this point, the image should look cleaner and more polished, without obvious artifacts from masking.

Step 5: Dodging & Burning in Photoshop for Final Contouring

Dodging and burning is where the image truly comes to life—this step enhances contours, sculpts the subject, and reinforces light directionality.

• Create two curves adjustment layers, one for brightening the image (dodging) and the other for darkening it (burning) before inverting them with a layer mask (pressing Ctrl+I)

• Using a white, soft, round brush with Flow set between 3-6%, paint on each layer mask as needed
• Dodge (Brighten) key areas:
  • The eyes (to create a natural glow and make them the focal point).
  • High points of the body where light would naturally hit.
  • Fine textures (scales, ridges) for better dimension.

• Burn (Darken) shadowed areas:
  • Undersides and crevices to deepen the contrast.
  • Background elements that distract from the subject.

Unlike heavy-handed contrast adjustments, this method allows for a more organic, painterly lighting effect.

Compared to our base image, you can see that the result is truly remarkable given it was all done with natural light!!

6. Limitations: When This Technique Falls Apart

As powerful as this method is, it’s not a universal fix. There are situations where post-production relighting just doesn’t hold up, either due to the way light behaves in water or the fundamental limitations of shooting in natural light. Understanding these limitations is just as important as knowing when to apply the technique.

1. Straight-On Shots Are Unforgiving

Unlike traditional strobes, which fire intense, directional bursts of light, this technique relies on gradual exposure adjustments to sculpt form. The problem? Straight-on shots—where the subject is directly facing the camera—lack natural shadow depth to begin with.

When shooting with strobes, even a flat-lit subject can be reshaped by shifting the angle of the lights. With natural light, however, the illumination is usually broad and uniform, leaving little to work with in post. Trying to force dramatic relighting onto a front-facing subject often results in unrealistic, plasticky effects, where the contours don’t match the actual structure of the subject.

Solution? Work with angled or side-lit shots whenever possible—these naturally introduce subtle shadow depth, making relighting feel more organic.

2. The Aperture Tradeoff: Why Shallow Depth Can Break the Effect

One of the biggest limitations of working with natural light underwater is that it often forces you to shoot at wider apertures than you would with strobes. This means shallower depth of field, which is fine for general subject isolation but problematic when trying to simulate controlled lighting.

With a real strobe, the entire subject is illuminated consistently, preserving edge sharpness and texture across its form. But if you’re shooting at f/2.8 or f/4, you might only have a sliver of the subject in crisp focus, while the rest falls into a natural blur.

This is a problem when applying relighting effects, since the artificial highlights and shadows don’t always align correctly with the soft-focus areas of the image. The result? A strange, detached look, where the relit portions of the image feel separate from the rest of the scene.

Solution? If possible, shoot at a mid-range aperture (f/5.6 to f/8) while still maintaining enough light for a clean exposure. If a wide aperture is unavoidable, be mindful of how depth of field will affect light falloff in post—sometimes, less dramatic adjustments are better.

3. Reflective or Translucent Subjects Don’t Play Nice

Some subjects—especially those with mirror-like scales (certain fish) or transparent bodies (jellies, larval fish, glass shrimp)—don’t respond well to post-production relighting.

The reason? These creatures don’t reflect light in a uniform way, and their surface properties are almost impossible to convincingly simulate. With strobes, light naturally bounces off their skin, creating specular highlights and natural rim-lighting effects. In post, however, applying fake highlights onto reflective surfaces rarely looks convincing.

Similarly, translucent or semi-transparent creatures pose a challenge because their internal structure affects how light passes through them. Strobes naturally reveal depth in these subjects by creating subtle internal shadows, but when attempting to “paint in” light digitally, the effect can feel flat or artificial.

Solution? Stick to subjects with solid form and texture—octopuses, moray eels, angelfish, lionfish, and groupers tend to work best. If working with reflective subjects, be extremely light-handed with adjustments—sometimes, a simple contrast boost is better than forced relighting.

4. It’s Not a Fix for Bad Composition or Poor Exposure

This technique is a refinement tool, not a rescue operation. If an image is poorly composed, overexposed, or fundamentally uninteresting, no amount of relighting will fix it.

Unlike strobes, which give you real-time control over lighting, this method is reactive, meaning you’re working with the light you had at the time of capture. If an image was shot with blown-out highlights, excessive backscatter, or weak subject separation, the final result will always be limited.

Solution? Nail your shot in-camera. Good composition, clean exposure, and controlled subject-background separation make all the difference. This technique can enhance an already great shot—but it won’t salvage a weak one.

7. Conclusion: Pushing Beyond the Limits of Natural Light

For years, underwater photographers have been locked into the same binary choice: shoot with natural light and accept its limitations, or use strobes and deal with the bulk, cost, and complexity.

This method offers a third option—one that takes the best of both worlds. By leveraging modern post-processing tools, we can recreate the depth, contrast, and structure of artificial lighting, all while keeping the freedom and simplicity of a natural-light setup.

But this isn’t just about mimicking strobes. What makes this technique valuable isn’t its ability to “fake” something—it’s the creative control it provides. Unlike strobes, which are locked into the moment of capture, this approach lets you shape light after the fact, adapting the final image to match your artistic vision.

At the same time, it’s not a magic trick. There are times when strobes will still be superior—especially for fast-moving subjects, highly reflective fish, or situations where absolute color accuracy is critical. But for many photographers, particularly those without access to expensive gear, this method opens up entirely new possibilities.

Who Is This Technique For?

• Freedivers & Travel Photographers – If you’re working without bulky strobes, this lets you retain lightweight mobility without sacrificing image quality.
• Budget-Conscious Shooters – No need for expensive lighting rigs—this approach gives you pro-level results with minimal gear.
• Anyone Looking to Push Their Editing Skills – Even if you own strobes, mastering post-processing light control expands your creative flexibility.

What This Means for Underwater Photography

With computational photography evolving faster than ever, we’re only beginning to scratch the surface of what’s possible. The tools we have today—CameraRAW’s object masking, Photoshop’s AI-assisted selections, non-destructive relighting techniques—are making it easier than ever to manipulate light in post without losing realism.

Where does this leave us? In a place where your final image is no longer limited by the tools you had at the moment of capture. Whether or not you have strobes, whether or not you had the “perfect” lighting conditions, you now have the ability to shape and refine your vision after the dive.

That, more than anything, is what makes this technique exciting. It’s not about replacing strobes—it’s about expanding the creative possibilities of natural-light shooting, pushing beyond the limits of what was once possible.